Connecting-circuit for magneto telephone-exchange systems.



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E. H. COLPITTS.

CONNECTING CIRGUIT FOR MAGNETO TELEPHONE EXCHANGE SYSTEMS.

APPLIGATION FILED. SEPT. 15, 1910.

1 029 593 Patented June 18, 1912.

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UNITED STATES PATENT OFFICE.

EDWIN HENRY GOLPITTS, OF EAST ORANGE, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, OF NEW YORK, N. Y., A CORPORATION OF ILLINOIS.

CONNECTING-CIRCUIT FOR MAGNE'IO TELEI HONE-EXCHANGE SYSTEMS.

Specification of Letters Patent.

Patented June 18, 1912.

Application filed September 15, 1910. Serial No. 582;248.

To all whom it may concern:

Be itknown that I, EDWIN H. CoLrlr'rs, subject of the King of Great Britain, residing at East Orange, in the county of Essex and State of New Jersey, have invented a certainnewaud useful Improvement in Connecting-Circuits for Magneto Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact description.

This irwention concerns signaling means employed in telephone exchange systems of the magneto type. Its object is to provide a connecting circuit of high transmission efficiency employing a common clearing-out signal for a pair of connected subscribers. Although such a system enables a reduction in the amount of apparatus involved, these systems as heretofore equipped have been open to the objection that one subscriber in actuating his magneto to give the discomnect signal frequently rings through the connecting circuit, and operates the bell of the line of the subscriber with whom he has been talking or causes disagreeablenoises in his telephone, according to the condition of such subscribers substation apparatus at the moment. This objectionable secondary current is in one type of connecting circuit due to the mutual inductance of the windings of the repeating coil and that of the windings of the clearing-out signal, induced current being created in the secondaries of each .of these devices upon the flow of ringing current through their primaries which currents are cumulative or in another type wherein the repeating coil is not present in the circuit, the objectionable second ary current is that created by the mutual inductance of the clearing-out signal alone. Another common defect in such systems is that the low resistance bridge across the line caused by either connected subscribers instrnments being included in circuit at the time the disconnect signal is sent out from the other connected line exerts a shunting effect on the high resistance clearing-out signal, frequently preventing its operation.

The present invention eliminates the first objection by taking advantage of the principle that electro mot-ive forces of equal strength and opposite direction created in a circuit neutralize each other, thereby preventing any flow of current, and eliminates the second by conductively separating the connecting circuit.

Since currents of two characters differing radically in frequency are GlnPlOXQ'tl, one for signaling and the other for talking, the above stated principle is utilized in the following manner to accomplish the desired results. The connecting circuit may be divided into a plurality of sections united by induction coils, one of which is arranged to operate a clearing-out signal, these induction coils being so constructed and arranged in the respective sections that upon the passage of ringing current through either sec tion eleetromotive forces are induced in the secondary section which oppose each other and thus prevent an appreciable current flow, means being associated with said sections to permit of the unaltered reproduction in one section of telephonic currents circulating in the other. Preferably the connecting circuit is split into two sections united inductively through a repeating coil. and a clearing-out signal, each section leading in series through a winding of each induction coil, the relation of the direction of the winding of one induction coil inonc section to the direction of the winding of the other in the same section being opposite to that existing between the windings of-the respective induction coils in the other section. Or, to state the same thing in different language, the inductive relation between the windings of the repeating coil is,

opposite to that between the windings of the clearing-out signal. It will be apparent: therefore that the electrolnoti re force ind need in the secondary winding in either induction coil due to the flow of ringing current in its primary, is opposite to that induced in the secondary of the other induction coil, thus preventing an appreciable current flow in the secondary section and thereby in the second subscribers line. The unaltered reproduction in the secondary section and thereby in the substation connected thcrewith of the telephonic currents circulating in the primary section is preferably provided for bybridging condensers around the respective windings of the clearing-out signal.

The accompanying drawing is a diagrammat-ic illustration of a telephone system equipped with a cord circuit of my inven tion.

The substations 1, 2 terminate at the central office in the usual springjacks J, J respectively, and include-apparatus that is too well known to require description.

The cord circuit C is in two sections inductively related at their inner ends and each terminating at its outer end in a plug P, P by means of which connection with substations 1, 2 respectively is established. While the repeating coil R is shown with four windings 7-, 1', 7' 1' we shall consider for convenience of description 1" and r as one winding and 1- 1* as another; it being understood of course that the illustration of the repeating coil is purely diagrammatic. The repeatingcoil R, as is well understood, reproduces in either section voice currents circulating in the other, the winding 1', 1'

being connected in series with plug P and I the winding 7*, r in series with plug P.

A clearing-out signal, which may be an an nunciator A, as shown, 13 provided with a pair of energizing windings, a, a, one con- .ductively connected with each section of the cord circuit and each in series with the winding of its respective side of the repeating coil, the said annunciator b'eing thereby responsive to signaling current circulating in either section originating at the respective substation. The inductive relation between the drop windings a, a is opposite to that between the repeating coil windings r, r considered asone and r 7' consldered as the other. This is indicated in the drawing by showing the windings a, a of the drop wound in opposite directions upon their common core and the repeating coil windings arranged as usual. Connected in series with winding 1', r of repeating coil R and in shunt of annunciator winding a is a condenser c. A condesner c is similarly associated with the other section. The condensers c, a afford paths around the respective drop windings a, a for the high frequency telephonic currents, said currents readily taking these paths because of the relatively high impedance of the alternative paths including the drop windings. On the other hand, these'condenser paths do not admit of the passage of an appreciable quantity of the low frequency signaling currents, which are thus compelled to traverse the drop windings and thus energize the drop.

By reference to the drawing it will be observed that upon the actuation of either magneto and the consequent passage of signaling current through the corresponding section made up of the repeating coil and annunciator windings in series, the potential across the terminals of the other section of the circuit is not appreciably raised; that is, the electromotive forces induced in the secondaries of the respective induction devices oppose each other with no appreciable resultant current flow. On the other hand, since, due to the presence of condensers c, 0 in shunt of drop windings a, a respectively, no appreciable amount of primary telephonic current circulates in either drop winding, it follows that practically no induced telephonic currents "are created in the secondary drop winding, and consequently telephonic currents circulating in the primary section of the connecting circuit are reproduced unaltered in the secondary section by the repeating coil R and are taken up in turn by the repeating coil of the sub station apparatus connected therewith.

Itis preferable to construct the respective induction coils with approximately equal mutual inductance at ringing frequencies; that is to say, the eleotromotive force induced in the secondary winding of either device due to the flow of signaling current in its primary should be approximately equal to that induced in the secondary of the other due to the flow of the same current in its primary winding, althoughit is apparent that to secure the desired result it is only necessary that the induced electromotive forces should be divided into approximately equal component parts which oppose each other, and that one induction coil need not be of equal inductance with the other providing it be associated with other means for raising or lowering its inductance to the required amount.

It will of course be understood that the term direction of winding used throughout the specification and claims really means the direction of the current flow, annunciators in practice being wound similarly to repeating coils, the method of connecting the windings in the circuit determining the direction of current flow and thereby their inductive effect.

It is not intended that the invention be limited to the embodiment shown, since the desired result may be secured by connecting the necessary induction and capacity instrumentalities in the connecting circuit in a variety of ways.

I claim l. A connecting circuit in a plurality of sections, induction coils having their primaries connected in series inone section and their secondaries connected in series in another, the relation of the direction of Winding of one secondary to-the other being opposite to that between the primaries, and shunt paths for telephonic current around the respective windings of one induction coil, said paths offering comparatively high resistance to the ringing current.

2. A-connecting circuit in a plurality of sections, a pair of induction coils with their corresponding windings in each section serially connected together, the inductive relation between the windings of the respective devices being opposite, thereby creating upon the passage of ringing current through the primary section elect-romotive forces of opposite polarity in the secondary section, and means for shunting telephonic current around the respective windings of one induction coil, said means ofiering comparatively high resistance to the ringing current.

3. A connecting circuit comprising sections united through a plurality of induction coils having their corresponding windings in each section connected together and in such a manner that due to their inductive relation the passage of ringing current through the primary section creates electromotive forces of opposite polarity in. the secondary section, and condensers for shunting telephonic current around the respective windings of one induction coil.

4;. A connecting circuit in two sections united inductively through two induction coils, eaclr sect-ion leading through corresponding windings of the respective induction coils in each section in series, the relation of the direction of winding of one induction coil in one section to the winding of the other induction coil in the same section' being opposite to that between the windings of the induction coils in the other section, means for impressing ringing and telephonic currents upon each section, said ringing current traversing a winding of each induction coil in each section, a. signal actuated upon the flow of said ringing current, and condensers for shunting said telephonic current around the windings of one induction coil in both sections.

5. A connecting circuit in two sections united through a repeating coil and annunciator, each section leading through corresponding windings of each induction coil in each section in series, the relation of the direction of winding of one induction coil in one section to the winding of the other in the same section being opposite to that between the windings of the induction coils of the other section, and a condenser in parallel with each annunciator winding in the respective sections.

6. A. connecting circuit consisting of two sections each leading serially through windings of a repeating coil and annunciator, the respective mutual inductances of said devices being approximately equal at ringing frequencies, and the annunciator windings being connected tov have an inductive relation opposite to the repeating coil windings, and a condenser in a divided circuit'with each annunciator Winding, whereby ringing current circulating in either section induces in the other electromotive forces approximately equal and opposite, while telephonic currents circulating in either repeating coil winding reproduce themselves in the other and are afforded a path around the corresponding annunciator winding through its associated condenser.

7. In a telephone exchange system, the combination with a connecting circuit in two sections, a repeating coil and an amiuneiator uniting said sections inductively, telephonic apparatus and means for generating ring ing current connected with each section, the arrangement of the windings of said repeating coil and annunciator being such that the ringing currents induced in the secondary section are approximately equal in strength and opposite in direction, and means for so altering the exterminative effect of said windings upon the flow of telephonic current as to permit of the unaltered reproduction or transfer of such current from either section to the other,

In witness whereof, I, hereunto subscribe my name this Mth day of September A. D., 1910.

EDWIN HENRY COLPTTTS.

Witnesses:

T. Q. BoozER; IRVING MACDONALD.

Copies ot'this patentmay be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. C. 

